Thalib, thank you very much for your reply! We all have things which are easier to practise with people on a certain level, and even in the "generous" dojo I found that people of third kyu and abouve generally went for each other for koshinage. Except for the really advanced people, who could practise koshinage with everybody. Time makes it easier to be generous.
I think it makes a big difference if this type of behaviour are approved of by the people who run the place or not, though. But you will always have a little bit of it. Nobody is perfect. Not even me.
Quite a few of you have misread my post, taking for granted that my question is whether I should leave the dojo in question or not. As I already said, I quit practising at this place one of two years ago. I have not regretted it for a minute! It was a good choice.
When I left, I think that actually things were changing for the better - cencerning my own position in that place, not in the general attitude. The people who were not very advanced when I came there and who I helped with their ukemi are starting to get really fun to practise with, so I do not really need the fancy clique that bad any more. Also, after an event in which I did a good performance some people suddenly started saying hello, who previously treated me like I was invisible... So this could have been the right timepoint to improve my position.
But, to what cost? I would have to learn how to be quicker than lightning in saying "onegai shimasu", and more importantly - I would need to avoid practising with some un-fancy people, as I will be judged partly by with who I practise.
I had the choice, I made my mind up. I do not go for "I either want less corruption, or better chance to participate in it".
Actually, I think if I was completely "pure" I could stay in this environment and remain "pure". But I also have this urge of a spot in the sun, if just a small one. This dojo takes out ugly sides of me that I do not want to reinforce.
Those of you who urge me not to quit aikido... maybe your concern should make me touched, but it actually makes me feel like "I it did not know it was a cult when I joined". If I do something else for a few years, it won't hurt me.